Thromboembolism is a serious and life threatening problem. The emboli can be sudden and massive and at other times they may be small and multiple. They can be any size and happen at any time.
When blood clots form in the venous circulation of the body they may move or embolize to the lungs. The clots typically embolize from the veins of the legs, pelvis, or inferior vena cava to the right heart cavities and thence into the pulmonary arteries. This results in right heart failure and decreased blood flow through the lungs with subsequent decreased oxygenation of the lungs, heart and the rest of the body. When clots enter the pulmonary arteries obstruction and spasm of the different arteries of the lung occurs which further decreases blood flow and gaseous exchange through the lung tissue resulting in pulmonary edema. All of these factors decrease the oxygen in the blood in the left heart. The oxygenated blood supplied by the coronary arteries to the musculature of both the left and right heart is insufficient for proper contractions of the muscle which further decreases the entire oxygenated blood flow to the rest of the body.
This malady is common and has many causes, among them are prolonged inactivity such as bed rest, dehydration, extensive surgery or protracted disease and many others in which the blood of the inferior peripheral major circulatory system may coagulate to varying degrees with permanent drainage problems.